Estimation of Heart Rate Recovery after StairClimbing Using aWrist-Worn Device

Heart rate recovery (HRR) after physical exercise is a convenient method to assesscardiovascular autonomic function. Since stair climbing is a common daily activity, usually followedby a slow walking or rest, this type of activity can be considered as an alternative HRR test.The present study explores the feasibility to estimate HRR parameters after stair climbing usinga wrist-worn device with embedded photoplethysmography and barometric pressure sensors.A custom-made wrist-worn device, capable of acquiring heart rate and altitude, was used to estimatethe time-constant of exponential decay t, the short-term time constant S, and the decay of heart ratein 1 min D. Fifty-four healthy volunteers were instructed to climb the stairs at three different climbingrates. When compared to the reference electrocardiogram, the absolute and percentage errors werefound to be ≤ 21.0 s ( 52.7%) for τ, ≤ 0.14 (≤ 19.2%) for S, and ≤ 7.16 bpm (≤ 20.7%) for D in 75%of recovery phases available for analysis. The proposed approach to monitoring HRR parameters inan unobtrusive way may complement information provided by personal health monitoring devices(e.g., weight loss, physical activity), as well as have clinical relevance when evaluating the efficiencyof cardiac rehabilitation program outside the clinical setting.